The present invention relates to a disk drive apparatus including a motor and a motor which is suitable to be used in a disk drive apparatus.
In recent years, a disk drive apparatus such as a hard disk drive apparatus (a HDD apparatus), an optical disk drive apparatus and a floppy disk drive apparatus includes a motor which alters current paths to windings by transistors so as to drive a disk. Conventionally, in this kind of motor, current paths to windings are altered by PNP-type bipolar power transistors and NPN-type bipolar power transistors.
FIG. 32 shows a conventional motor. The operation of the motor is briefly described below. A rotor 2011 has a field part formed by a permanent magnet. Three position detecting elements of a position detector 2041 detect the magnetic field of the field part of the rotor 2011. In other words, the position detector 2041 generates two sets of three-phase voltage signals, Kp1, Kp2 and Kp3, and Kp4, Kp5 and Kp6, from the three-phase output signals of the three position detecting elements in response to the rotation of the rotor 2011. A first distributor 2042 produces three-phase low-side activation control signals Lp1, Lp2 and Lp3 responding with the voltage signals Kp1, Kp2 and Kp3. The first distributor 2042 supplies the low-side activation control signals Lp1, Lp2 and Lp3 to the bases of low-side NPN-type bipolar power transistors 2021, 2022 and 2023 so as to control the activation of the NPN-type bipolar power transistors 2021, 2022 and 2023. A second distributor 2043 produces three-phase high-side activation control signals Mp1, Mp2 and Mp3 responding with the voltage signals Kp4, Kp5 and Kp6. The second distributor 2043 supplies the high-side activation control signals Mp1, Mp2 and Mp3 to the bases of high-side PNP-type bipolar power transistors 2025, 2026 and 2027 so as to control the activation of the PNP-type bipolar power transistors 2025, 2026 and 2027. As a result, the current paths to three-phase windings 2012, 2013 and 2014 are controlled so as to be opened or closed.
In this conventional configuration, power losses of the power transistors are large, and the power efficiency of the motor is very low. The NPN-type bipolar power transistors 2021, 2022 and 2023 and the PNP-type bipolar power transistors 2025, 2026 and 2027 supply drive voltages to the windings 2012, 2013 and 2014 by controlling the voltage drops across the emitters and the collectors of them in an analogue manner. A residual voltage in each power transistor is large, and a large power loss and a heat are generated by the product of the residual voltage and a drive current of each power transistor. As a result, the power efficiency of the motor is low, and the power consumption of the disk drive apparatus is large. In addition, the power loss and the heat of the disk drive apparatus raise a temperature of a disk, and bit errors occur frequently during recording and reproducing a signal on/from a disk.
U.S. Pat. No. 5,982,118 and U.S. Pat. No. 5,473,232 disclose motors wherein power transistors are subjected to PWM operation (PWM: Pulse Width Modulation) to reduce power consumption. However, the motor configurations in accordance with U.S. Pat. No. 5,982,118 and U.S. Pat. No. 5,473,232 cause a very large high-frequency switching noise owing to the PWM operation of the power transistors. This switching noise disturbs a reproduction signal from the head and significantly raises the bit error rate of the reproduction signal of the disk drive apparatus.
In a magnetic disk drive apparatus (such as a HDD apparatus), and an optical disk drive apparatus (such as a DVD apparatus), a high-frequency noise must be minimized to reproduce stably a signal from a high-density disk. However, when power transistors execute PWM operation, a very large high-frequency switching noise occurs. Hence, the reliability of the reproduction signal of the disk drive apparatus is significantly lowed by the high-frequency noise. It is thus difficult to allow power transistors to execute PWM operation in a disk drive apparatus.
It is therefore an object of the present invention to solve the above-mentioned problems respectively or concurrently and to provide a highly reliable disk drive apparatus, which has a low power consumption and a low noise, and a motor suitable to drive a disk or the like.
A disk drive apparatus in accordance with the present invention comprises:
head means for reproducing a signal from a disk;
processing means for processing an output signal from said head means and outputting a processed signal;
a rotor, having a field part which generates field fluxes, for driving said disk;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said disk; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces at least a slew-rate switching signal which responds with said switching pulse signal at a control terminal side of at least one power transistor among said Q first power transistors and said Q second power transistors, said at least a slew-rate switching signal having a smoothed voltage slope in at least one of rising and falling slopes, and causes said at least one power transistor to follow said at least a slew-rate switching signal, thereby supplying a high-frequency switching drive voltage signal to one terminal of said Q-phase windings, said high-frequency switching drive voltage signal having smoothed voltage slopes and responding with said current detection signal and said command signal.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a disk drive apparatus with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. So the acoustic noise and the vibration of the disk are reduced remarkably. Furthermore, since at least one of the power transistors executes high-frequency switching operation responding with the switching pulse signal of the switching operation means, the slew-rate switching signal is produced easily. Still further, the power transistor is caused to follow the slew-rate switching signal, and supplies the drive voltage signal to one of the windings. Hence, the drive voltage signal to the winding becomes a high-frequency voltage signal which has adequate voltage slopes responding with the slew-rate switching signal. So the high-frequency noise due to the high-frequency switching operation of the power transistor is reduced significantly. As a result, bit errors of the reproduction signal in the disk drive apparatus is reduced significantly. Therefore, a high-performance disk drive apparatus with a low power consumption, a low error rate of the reproduction signal, a low acoustic noise and a small vibration is realized.
A disk drive apparatus in accordance with another aspect of the present invention comprises:
head means for reproducing a signal from a disk;
processing means for processing an output signal from said head means and outputting a processed signal;
a rotor, having a field part which generates field fluxes, for driving said disk;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said disk; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
each of said Q first power transistors is a first NMOS-FET power transistor for forming a current path from the positive terminal side of said voltage supplying means to one of said Q-phase windings,
each of said Q second power transistors is a second NMOS-FET power transistor for forming a current path from the negative terminal side of said voltage supplying means to one of said Q-phase windings,
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces at least a slew-rate switching signal at a control terminal side of at least one power transistor among said first NMOS-FET power transistors responding with said switching pulse signal, said at least a slew-rate switching signal having a smoothed voltage slope in at least one of rising and falling slopes, and causes said at least one power transistor to follow said at least a slew-rate switching signal, thereby supplying a high-frequency switching drive voltage signal to one terminal of said Q-phase windings, said high-frequency switching drive voltage signal having smoothed voltage slopes and responding with said current detection signal and said command signal.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a disk drive apparatus with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q electrical degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. So the acoustic noise and the vibration of the disk are reduced remarkably. Furthermore, since at least one of the power transistors executes high-frequency switching operation responding with the switching pulse signal of the switching operation means, the slew-rate switching signal is produced easily. Still further, at least one of the first N-channel FET power transistors is caused to follow the slew-rate switching signal, and supplies the drive voltage signal to one of the windings. Hence, the drive voltage signal to the winding becomes a high-frequency voltage signal which has adequate voltage slopes responding with the slew-rate switching signal. So the high-frequency noise due to the high-frequency switching operation of the first N-channel FET power transistor is reduced significantly. Furthermore, N-channel FET power transistors attain high-frequency switching operation with a low resistance during the ON period. Still further, the N-channel FET power transistors are easily integrated with other resistors and transistors on a small semiconductor chip. Therefore, a high-performance disk drive apparatus with a low power consumption, a low error rate of the reproduction signal, a low acoustic noise and a small vibration is realized.
A disk drive apparatus in accordance with still another aspect of the present invention comprises:
head means for reproducing a signal from a disk;
processing means for processing an output signal from said head means and outputting a processed signal;
a rotor, having a field part which generates field fluxes, for driving said disk;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said disk; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces two slew-rate switching signals which responds with said switching pulse signal at control terminal sides of two of said Q first power transistors, each of said two slew-rate switching signals having a smoothed voltage slope in at least one of rising and falling slopes, and causes said two of said Q first power transistors to perform high-frequency switching substantially simultaneously responding with said two slew-rate switching signals, when said two of said Q first power transistors alter current paths to said Q-phase windings while at least one of said Q second power transistors remains ON without ON-OFF switching.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a disk drive apparatus with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. In particular, when the two of the first power transistors alter current paths to the Q-phase windings, the two of the first power transistors are caused to perform high-frequency switching operation substantially simultaneously responding with the switching pulse signal, whereby the alteration of current paths is smoothened. Hence, the acoustic noise and the vibration of the disk are reduced greatly. Furthermore, since the two slew-rate switching signals which responds with the switching pulse signal of the switching operation means are produced at the control terminal sides of the two of the first power transistors, the two of the first power transistors execute high-frequency switching operation responding with the two slew-rate switching signals. Hence, the drive voltage signals to the windings become high-frequency voltage signals each of which have adequate voltage slopes responding with each of the two slew-rate switching signals. So the high-frequency noise due to the high-frequency switching operation of the power transistors is reduced significantly. As a result, bit errors of the reproduction signal in the disk drive apparatus are reduced significantly. Therefore, a high-performance disk drive apparatus with a low power consumption, a low error rate of the reproduction signal, a low acoustic noise and a small vibration is realized.
Still further, since the heat generation of the power transistors is very low, the power transistors can be integrated easily with other semiconductor elements (resistors and transistors) on a small one-chip silicon substrate. In particular, an N-channel FET power transistor can realize a high-performance power transistor in a smaller chip area than a P-channel FET power transistor, and the N-channel FET power transistor is suitable to a power transistor. As a result, a low-cost disk drive apparatus is realized.
Still further, in case that the switching control means produces a single switching pulse signal which responds with the comparison result between the current detection signal and the command signal, the slew-rate switching signals responding with the single switching pulse signal are produced easily, and one or two of the first power transistors are caused to perform high-frequency switching operation substantially simultaneously responding with the slew-rate switching signal. Hence, while the high-frequency drive voltage signals to the windings have adequate voltage slopes in at least one of the rising and falling slopes, the composed current to the windings is controlled accurately responding with the command signal. As a result, a high-performance disk drive apparatus with a low current ripple, a small vibration, a low acoustic noise and a low power consumption is realized.
In addition, in case that the position detecting means produces position signals responding with the terminal voltages of the Q-phase windings, it is unnecessary to use position detecting elements for detecting the rotational position. Furthermore, in case that the commanding means produces a command signal responding with the rotational speed of the disk by using a detected pulse signal (a position signal) which responds with the terminal voltages of the windings, no speed detecting element is required. Therefore, a low-cost disk drive apparatus with reduced components is realized.
In addition, the position detecting means stops the detection operation of the terminal voltages of the windings during stop periods which include at least one of the rising and falling slopes of the slew-rate switching signal, and the position detecting means carries out the detection operation of the terminal voltages of the windings during the rest periods except the stop periods. This eliminates the influence of the high-frequency voltage noise due to the high-frequency switching drive voltage signals which have slew-rate slopes, whereby the position detecting means can accurately detect the terminal voltages of the windings, such as the zero-crossing point of a back electromotive force. In particular, in case that a noise eliminating signal is produced by responding with the switching pulse signal, it is possible to produce accurately the noise eliminating signal which is synchronized with the slew-rate switching signal. Then the influence of the high-frequency noise due to the high-frequency switching operation can be eliminated easily. Hence, the alteration of current paths to the windings can be stabilized, and the rotation of the disk can be stable. Furthermore, the position detecting means produces the detected pulse signal (the position signal) at accurate timing, whereby the rotational speed of the disk can be controlled accurately by using the detected pulse signal. As a result, the disk drive apparatus can accurately record and/or reproduce a signal on/from a high-density disk.
A motor in accordance with the present invention comprises:
a rotor having a field part which generates field fluxes;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said rotor; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces at least a slew-rate switching signal which responds with said switching pulse signal at a control terminal side of at least one power transistor among said Q first power transistors and said Q second power transistors, said at least a slew-rate switching signal having a smoothed voltage slope in at least one of rising and falling slopes, and causes said at least one power transistor to follow said at least a slew-rate switching signal, thereby supplying a high-frequency switching drive voltage signal to one terminal of said Q-phase windings, said high-frequency switching drive voltage signal having smoothed voltage slopes and responding with said current detection signal and said command signal.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a motor with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. So the acoustic noise and the vibration of the rotor are reduced remarkably. Furthermore, since at least one of the power transistors executes high-frequency switching operation responding with the switching pulse signal of the switching operation means, the slew-rate switching signal is produced easily. Still further, the power transistor is caused to follow the slew-rate switching signal, and supplies the drive voltage signal to one of the windings. Hence, the drive voltage signal to the winding becomes a high-frequency voltage signal which has adequate voltage slopes responding with the slew-rate switching signal. So the high-frequency noise due to the high-frequency switching operation of the power transistor is reduced significantly. Therefore, a high-performance motor with a low power consumption, a low acoustic noise and a small vibration is realized.
A motor in accordance with another aspect of the present invention comprises:
a rotor having a field part which generates field fluxes;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said rotor; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
each of said Q first power transistors is a first NMOS-FET power transistor for forming a current path from the positive terminal side of said voltage supplying means to one of said Q-phase windings,
each of said Q second power transistors is a second NMOS-FET power transistor for forming a current path from the negative terminal side of said voltage supplying means to one of said Q-phase windings,
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces at least a slew-rate switching signal at a control terminal side of at least one power transistor among said first NMOS-FET power transistors responding with said switching pulse signal, said at least a slew-rate switching signal having a smoothed voltage slope in at least one of rising and falling slopes, and causes said at least one power transistor to follow said at least a slew-rate switching signal, thereby supplying a high-frequency switching drive voltage signal to one terminal of said Q-phase windings, said high-frequency switching drive voltage signal having smoothed voltage slopes and responding with said current detection signal and said command signal.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a motor with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q electrical degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. So the acoustic noise and the vibration of the rotor are reduced remarkably. Furthermore, since at least one of the power transistors executes high-frequency switching operation responding with the switching pulse signal of the switching operation means, the slew-rate switching signal is produced easily. Still further, at least one of the first N-channel FET power transistors is caused to follow the slew-rate switching signal, and supplies the drive voltage signal to one of the windings. Hence, the drive voltage signal to the winding becomes a high-frequency voltage signal which has adequate voltage slopes responding with the slew-rate switching signal. So the high-frequency noise due to the high-frequency switching operation of the first N-channel FET power transistor is reduced significantly. Furthermore, N-channel FET power transistors attain high-frequency switching operation with a low resistance during the ON period. Still further, the N-channel FET power transistors are easily integrated with other resistors and transistors on a small semiconductor chip. Therefore, a high-performance motor with a low power consumption, a low acoustic noise and a small vibration is realized.
A motor in accordance with still another aspect of the present invention comprises:
a rotor having a field part which generates field fluxes;
Q-phase windings (Q is an integer of 3 or more);
voltage supplying means, including two output terminals, for supplying a DC voltage;
power supplying means having Q first power transistors and Q second power transistors, each of said Q first power transistors forming a current path between one output terminal side of said voltage supplying means and one of said Q-phase windings, and each of said Q second power transistors forming a current path between the other output terminal side of said voltage supplying means and one of said Q-phase windings;
position detecting means for producing a position signal which responds with the rotation of said rotor;
activation operation means for controlling active periods of said Q first power transistors and said Q second power transistors responding with an output signal of said position detecting means, each of said active periods being larger than the period of 360/Q electrical degrees;
commanding means for producing a command signal which responds with a rotational speed of said rotor; and
switching operation means for causing at least one of said Q first power transistors and said Q second power transistors to perform high-frequency switching responding with said command signal; and that
said switching operation means includes:
current detecting means for producing a current detection signal which responds with or corresponds to a composed current to said Q-phase windings from said voltage supplying means, and
switching control means for producing a switching pulse signal which responds with said current detection signal and said command signal, and
said activation operation means produces two slew-rate switching signals which responds with said switching pulse signal at control terminal sides of two of said Q first power transistors, each of said two slew-rate switching signals having a smoothed voltage slope in at least one of rising and falling slopes, and causes said two of said Q first power transistors to perform high-frequency switching substantially simultaneously responding with said two slew-rate switching signals, when said two of said Q first power transistors alter current paths to said Q-phase windings while at least one of said Q second power transistors remains ON without ON-OFF switching.
With this configuration, since at least one of the Q first power transistors and the Q second power transistors performs high-frequency switching operation, the power losses of the power transistors are very small. In other words, the heat generation of the power transistors is very low, and a motor with a low power consumption is realized. In addition, since each of the active periods of the power transistors is larger than the period of 360/Q degrees and the composed current to the Q-phase windings is controlled responding with the command signal, the fluctuation of the generated drive force is remarkably reduced. In particular, when the two of the first power transistors alter current paths to the Q-phase windings, the two of the first power transistors are caused to perform high-frequency switching operation substantially simultaneously responding with the switching pulse signal, whereby the alteration of current paths is smoothened. Hence, the acoustic noise and the vibration of the rotor are reduced greatly. Furthermore, since the two slew-rate switching signals which responds with the switching pulse signal of the switching operation means are produced at the control terminal sides of the two of the first power transistors, the two of the first power transistors execute high-frequency switching operation responding with the two slew-rate switching signals. Hence, the drive voltage signals to the windings become high-frequency voltage signals each of which have adequate voltage slopes responding with each of the two slew-rate switching signals. So the high-frequency noise due to the high-frequency switching operation of the power transistors is reduced significantly. Therefore, a high-performance motor with a low power consumption, a low acoustic noise and a small vibration is realized.
Still further, since the heat generation of the power transistors is very low, the power transistors can be integrated easily with other semiconductor elements (resistors and transistors) on a small one-chip silicon substrate. In particular, an N-channel FET power transistor can realize a high-performance power transistor in a smaller chip area than a P-channel FET power transistor, and the N-channel FET power transistor is suitable to a power transistor. As a result, a low-cost motor is realized.
Still further, in case that the switching control means produces a single switching pulse signal which responds with the comparison result between the current detection signal and the command signal, the slew-rate switching signals responding with the single switching pulse signal are produced easily, and one or two of the first power transistors are caused to perform high-frequency switching operation substantially simultaneously responding with the slew-rate switching signal. Hence, while the high-frequency drive voltage signals to the windings have adequate voltage slopes in at least one of the rising and falling slopes, the composed current to the windings is controlled accurately responding with the command signal. As a result, a high-performance motor with a low current ripple, a small vibration, a low acoustic noise and a low power consumption is realized.
In addition, in case that the position detecting means produces position signals responding with the terminal voltages of the Q-phase windings, it is unnecessary to use position detecting elements for detecting the rotational position. Furthermore, in case that the commanding means produces a command signal responding with the rotational speed of the rotor by using a detected pulse signal (a position signal) which responds with the terminal voltages of the windings, no speed detecting element is required. Therefore, a low-cost motor with reduced components is realized.
In addition, the position detecting means stops the detection operation of the terminal voltages of the windings during stop periods which include at least one of the rising and falling slopes of the slew-rate switching signal, and the position detecting means carries out the detection operation of the terminal voltages of the windings during the rest periods except the stop periods. This eliminates the influence of the high-frequency voltage noise due to the high-frequency switching drive voltage signals which have slew-rate slopes, whereby the position detecting means can accurately detect the terminal voltages of the windings, such as the zero-crossing point of a back electromotive force. In particular, in case that a noise eliminating signal is produced by responding with the switching pulse signal, it is possible to produce accurately the noise eliminating signal which is synchronized with the slew-rate switching signal. Then the influence of the high-frequency noise due to the high-frequency switching operation can be eliminated easily. Hence, the alteration of current paths to the windings can be stabilized, and the rotation of the rotor can be stable. Furthermore, the position detecting means produces the detected pulse signal (the position signal) at accurate timing, whereby the rotational speed of the rotor can be controlled accurately by using the detected pulse signal. As a result, the motor can accurately control the rotational speed.
These and other configurations and operations will be described in detail in the explanations of embodiments.